1. Field of the Invention
The present invention relates to a power saving LED (Light Emitting Diode) display board system; and, more particularly, to a power saving LED display board system reducing energy usage for light emission of LEDs to increase energy efficiency, simplifying electric wirings therein, facilitating white-balance adjustment on the LEDs and providing stable light emission of the LEDs.
In recent, display boards employing LEDs (hereinafter, referred to as “LED display boards”) are being widely used as various information transfer media, e.g., advertisement boards, public information boards and briefing boards, because they have distinctive features, from conventional display boards, in that time-varying characters and graphics can be displayed thereon. Further, since the LED display boards can show information in real time, they are being in a spotlight as information transfer media for real-time information on industrial spots or news.
In an LED display board, red, green and blue LEDs are combined to form pixels and white-balance of each pixel is adjusted to thereby express colors naturally.
In general, for white-balance adjustment, two red LEDs having relatively low color density and a green and a blue LED having relatively high color densities are combined to form a pixel.
Further, a plurality of pixels, e.g., 256 pixels, forms an LED module, and a power supply simultaneously supplies an electric power to a plurality of LED modules. An LED display board system is constructed by extending the above-described configuration according to the size of a screen.
That is, as shown in FIG. 1, a plurality of LED modules 30 receives an electric power from a power supply 20, and in case of enlarging the size of a display board, units each having a power supply 20 and a plurality of LED modules 30 are added. The power supplies 20 are connected to a common power source 10 to receive AC (Alternating Current) powers therefrom.
Further, as described above and shown in FIG. 2, each pixel has four LEDs including two red LEDs, one green LED and one blue LED. The four LEDs commonly receive an electric power of 3.5 V from a power supply, e.g., the power supply 20 of FIG. 1.
Hence, a voltage-dividing resistor R is connected to the input terminal of each red LED having a relatively low color density such that the electric power of 3.5 V is dropped to an electric power of 1.5 V and then supplied to the red LED.
However, since not only electric wirings for supplying an electric power from each power supply 20 to the LED modules 30 are complicated as shown in FIG. 1 but also much amount of electric current needs to be supplied from each power supply 20 to the LED modules 30, the above-described prior art has a drawback in that energy loss due to resistance of the wirings themselves increases.
Moreover, since an identical operating power is applied to all the LEDs of different colors by the single power supply 20 and the voltage-dividing resistors R are used for the red LEDs having relatively low color density as shown in FIG. 2, energy loss occurs at the voltage-dividing resistors R and much amount of heat is generated during the energy consumption at the voltage-dividing resistors R.